1. Field of the Invention
The present invention relates to an image capture device that can track a feature in a moving picture. The present invention is applicable to digital cameras, camcorders, personal digital assistants with face detection function and tracking function that uses color information.
2. Description of the Related Art
As an exemplary image capture device with the face detection function, Japanese Patent Application Laid-Open Publication No. 2007-42072 proposes a device for continuing to track a target face, which the device has once lost sight of, in a moving picture by estimating the location of that face.
To get such tracking done, the image capture device of Japanese Patent Application Laid-Open Publication No. 2007-42072 stores in advance not just information about the face detected but also information about what surrounds the face (which will be referred to herein as “environment information”). The environment information is acquired from an area that has been defined based on its location with respect to the face. In the current frame of the moving picture, the current location of the face is roughly estimated based on its past location. In the vicinity of the estimated location, a location that is closest to the environment information stored is searched for. And based on such a location that has been determined to be closest and the relative locations of the environment information and the face, the location of the face in the current frame of the moving picture can be estimated.
The image capture device of Japanese Patent Application Laid-Open Publication No. 2007-42072 roughly estimates the current location of the face based on its past location and searches for a location that is closest to the environment information in the vicinity of the estimated location. That is to say, the search range of that location closest to the environment information is determined by how accurately the current rough location of the face can be estimated. This means that the accuracy of estimating the current exact location of the face depends on the accuracy of estimating the current rough location of the face. And if the accuracy of estimating the current rough location of the face were poor, then no location that is close enough to the environment information could be found or even a wrong location might be detected, too. In that case, the current exact location of the face could not be estimated or a wrong location might be detected.
It is therefore an object of the present invention to provide an image capture device that can track a feature highly accurately in a moving picture even in a situation where the feature being tracked cannot be searched for accurately enough.